1. Field of Invention
The present disclosure relates to a temperature compensated oscillator. More particularly, the present disclosure relates to a micro electro mechanical systems (MEMS) temperature compensated oscillator.
2. Description of Related Art
An oscillator is an electronic device used to generate a periodic signal (such as a square wave or a sine wave). Currently, a common electric device, such as a signal generator, a frequency synthesizer, or a phase lock loop, uses an oscillator to provide periodic signals required for operation.
A quartz oscillator is one of the most popular oscillators presently. Since the quartz oscillator has advantages of simple structure and low cost, the quartz oscillator is popularly used in various electronic products. However, due to the limitation of mechanical cutting operations and polishing operations used to process quartz crystals, it is not easy to fabricate a quartz element having a small size and a high frequency. Therefore, a trend of using a micro electro mechanical systems (MEMS) oscillator to replace the quartz oscillator is gradually developed.
For fabricating the MEMS oscillator, a semiconductor technology is first used to fabricate a resonator structure, and then by using a System in Package (SiP) technology is used to integrate a controller and the resonator structure in a single chip package. Since the MEMS resonator is formed from silicon the processes for fabricating the MEMS oscillator are compatible with semiconductor processes. Also, the MEMS oscillator has various oscillation modes, and thus a high frequency element with a small size can be fabricated thereby. However, since being affected by a Temperature Coefficient of Young's Modulus (TCE), a Coefficient of Thermal Expansion (CTE), etc. of the MEMS resonator, the frequency of the MEMS resonator is drifted with temperature changes. Therefore, a temperature compensation design is needed to increase the stability of the frequency of the MEMS resonator